In order to implement a web application using Spring Boot, the following build tools need to be downloaded and installed:

• To install Java Development Kit (JDK) 8, download it from its official page at http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
• To install Maven 3, download it from its official page at https://maven.apache.org/download.cgi

• To install IntelliJ IDEA, download it from its official page at https://www.jetbrains.com/idea/download/
• To install Spring Tool Suite (STS), download it from its official page at https://spring.io/tools

The source code for this chapter can be found at https://github.com/PacktPublishing/Spring-Boot-2.0-Projects-Fundamentals-of-Spring-Boot-2.0, under the Chapter02 directory.

In this section, readers will get an overview of the web application being developed. The requirements, design, and implementation details will be discussed in brief.

A web application is exposed to multiple concurrent users over a public or private network as opposed to a standalone application. Let's get started developing a basic web application that uses the well known Model-view-controller (MVC) pattern to build a three-tier application. The MVC pattern is known for its separation of concerns by decoupling presentation logic (what the user sees in a browser), routing and business logic (what the application needs to accomplish), and persistence (where the data is finally...

In this section, readers will learn what JPA is, as well as how Spring Data JPA helps simplify the development of applications with database persistence.

JPA provides object/relation mapping capabilities to enable mapping between relational database tables and Java objects in order to ease persistence in Java applications. JPA consists of the following features:

• A query language to enable querying from relational database tables in order to retrieve Java objects
• A JPA Criteria API, which can be used to generate queries dynamically
• A set of metadata defined with XML Java annotations in order to successfully map relational database table columns...

In this section, we will explain in detail what a template engine is, and how to use Spring Thymeleaf to implement the view presentation.

Standard Java Enterprise Edition (Java EE) applications used JSPs to generate presentation views for the end user. JSP is a mature technology that enables users to use embedded Java code as well as Java Server Tag Library (JSTL) elements, which will, in turn, execute Java code to generate a presentation view. All JSPs are eventually compiled as a servlet.

But mixing this Java code with presentation-specific code (HTML, CSS, and many more) is cumbersome and makes separation of concern difficult. Furthermore, presentation views...

Controllers are the integration point between the model and view in the MVC paradigm. They act like glue that binds together everything while taking care of business logic execution and routing. The following Maven starter dependency needs to be added to enable Spring Web MVC:

<dependencies>
   ...
   <dependency>
       <groupId>org.springframework.boot</groupId>
       <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
</dependencies>

The preceding dependency will import servlet, Spring, and Tomcat dependencies to enable successfully writing servlet-based web applications using Spring.

This web application has used Spring Security to authenticate users and to authorize them to submit comments. The Maven Spring Security starter needs to be specified as follows to enable Spring Security in the web application:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-security</artifactId>
    </dependency>
</dependencies>

The following is the Spring Security configuration:

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {

    @Autowired
    private UserService userDetailService;

    @Override
    public void configure(WebSecurity web) throws Exception {
        web.ignoring().antMatchers("/h2-console/**");
    }

    @Override
    protected void...

When everything is put together, build and run the Retro Board, which we will be able to access using the http://<host>:<port> URL.

There are several ways to run a Spring Boot application, some of which are:

• Running the Spring Boot application main class using an IDE
• Building a JAR or WAR file using the following Maven command and then running:

$ mvn clean install
$ java -jar target/<package-name>.[jar|war]

• Running using the Spring Boot Maven plugin:

$ mvn clean spring-boot:run

After running, the Retro Board web application will launch the login screen as follows:

This login screen is the default login screen for form logins in Spring Security. A username/password combination created in SecurityConfig can be used to log in to the system. After successful login, the user will be routed to the comments page, which is as follows...

Congratulations on completing this chapter, where the skills and knowledge required to build a basic web application were discussed in detail. This chapter started off by explaining what a web application is and how a web application can benefit from MVC patterns in terms of both development and maintenance. It talked about the requirements of a web application being developed and used a UML use case diagram to explain the requirement visually.

This chapter also explained how to write the domain model of an application based on the requirements, how to write data repositories for it, how to test those for their correct functioning, and so on. It also discussed how to encapsulate business logic inside services and test them effectively to make sure everything works correctly.

Subsequently, the chapter talked about how to write presentation views to create and display comments...

Please answer the following questions to see whether you have successfully mastered this chapter:

1. What is a web application?
2. What is an MVC pattern?
3. What is a relational database?
4. What is JPA?
5. How is the @Entity annotation used in JPA?
6. What is a template engine?
7. What is Spring Security used for?

In order to improve your knowledge of Spring Web MVC and Spring Security, the following books are recommended and will be helpful in the coming chapters:

• Spring MVC: Designing Real-World Web Applications: https://www.packtpub.com/application-development/spring-mvc-designing-real-world-web-applications
• Spring Security - Third Edition: https://www.packtpub.com/application-development/spring-security-third-edition